1. Field of the Invention
The invention is based on a power breaker having at least one quenching chamber, and in particular, to a power breaker having two stationary consumable contact arrangements and a moving bridging contact which electrically conductively connects the consumable contact arrangements.
2. Discussion of Background
Laid-open specification DE 42 00 896 A1 discloses a power breaker which has a quenching chamber with two stationary consumable contacts which are at a distance from one another. The quenching chamber is filled with an insulating gas, preferably SF.sub.6 gas under pressure. When the quenching chamber is in the connected state, the two consumable contacts are electrically conductively connected to one another by means of a moving bridging contact. The bridging contact concentrically surrounds the consumable contacts, which are of cylindrical design. The bridging contact and the two consumable contacts form a power current path, on which current acts only during disconnection. During disconnection, the bridging contact slides down from a first of the consumable contacts and draws an arc which initially burns between the first consumable contact and the end of the bridging contact facing it. As soon as this end reaches the second consumable contact, the arc base commutates from the end of the bridging contact onto the second consumable contact. The arc now burns between the two consumable contacts and is blown until the arc is quenched. The pressurized insulating gas which is required for blowing is, as a rule, produced by means of a blowout piston which is connected to the moving bridging contact.
In addition, this power breaker has a rated current path in parallel with the power current path, which rated current path carries the operational current when the power breaker is switched on. The rated current path is arranged concentrically around the power current path. The bridging contact is in this case mechanically rigidly connected to a moving rated current contact which is arranged in the rated current path. During disconnection, the rated current path is interrupted first, and the current to be interrupted then commutates onto the power current path where, as described above, an arc is then struck and is then quenched.
Because of its dimensions, the bridging contact has a comparatively large mass to be moved, which must first be accelerated and then braked during switching processes. The power breaker drive has to provide the power required for this process.
Laid-open specification DE 31 27 962 A1 discloses a further power breaker which has a quenching chamber with two stationary consumable contacts at a distance from one another. The quenching chamber is filled with an insulating gas, preferably SF.sub.6 gas under pressure. When the quenching chamber is in the connected state, the two consumable contacts are electrically conductively connected to one another by means of a moving bridging contact. The bridging contact concentrically surrounds the consumable contacts, which are of cylindrical design. The bridging contact is in this case at the same time designed as a rated current contact. The disconnection process of this power breaker is similar to that for the power breaker described above.
Because of its dimensions, this bridging contact likewise has a comparatively large mass to be moved, which must be accelerated and braked during switching processes. The power breaker drive must provide the power required for this purpose.
Patent Specification CH 651 420 discloses a power breaker which has a stationary blowout volume into which insulating gas is fed which is produced from a pressure source and is subject to high pressure. The high pressure is reduced during entry into the blowout volume, so that only a comparatively low blowout pressure is available for blowing out the arc.
Patent Specification CH 644 969 discloses a power breaker which has two series-connected blowout volumes. The pure insulating gas which is present in the first blowout volume is compressed by means of a piston during the disconnection movement of the moving power contact. In addition, hot gas which is heated in the arc zone flows from the arc into this first blowout volume, is mixed with the pure insulating gas to form a gas mixture, and thus increases the pressure in this first blowout volume. After a predetermined movement of the moving power contact, a second blowout volume is disconnected from the first blowout volume, and the gas mixture in the two blowout volumes is then further compressed as a function of the movement. During the further course of the disconnection movement, both blowout volumes interact, independently of one another, with the pressure in the arc zone of this power breaker. However, it is necessary to take account of the fact that gas mixture pressures in approximately the same order of magnitude range prevail in each case at the same point in time in the two blowout volumes, it being possible, because of the larger cross section of the connection of the first blowout volume, which is somewhat reduced in terms of volume, to the arc zone for somewhat higher pressures to occur momentarily in this first blowout volume than in the second blowout volume. These pressure differences are caused just by the thermal effects of the arc. The rise in pressure in the two blowout volumes will differ from one disconnection to the next, depending on the magnitude of the current to be interrupted and on the instant of contact separation.